1. Field of the Invention
The present invention relates to a manufacturing method of a photoelectric conversion device.
2. Description of the Related Art
In recent years, inexpensive digital cameras and video cameras providing high image quality have become widespread. The photoelectric conversion device used in digital cameras and video cameras includes a CCD type and a MOS type photoelectric conversion device. A MOS type photoelectric conversion device includes a photoelectric conversion region including a MOS transistor and a photodiode and a peripheral circuit region including a MOS transistor outputting signals of the photoelectric conversion region and driving the MOS transistor arranged in the photoelectric conversion region. Those photoelectric conversion region and peripheral circuit region can be manufactured through a common step by a CMOS manufacturing process.
Japanese Patent Application Laid-Open No. H09-055440 describes contact structure used at an occasion of manufacturing an SRAM by the CMOS manufacturing process. Specifically, in structure, a semiconductor region is electrically connected to a gate electrode with an electroconductor buried in a hole arranged in an interlayer insulation layer and a plurality of layers of an electroconductor arranged in a hole arranged in an interlayer insulation layer are stacked. In addition, Japanese Patent Application Laid-Open No. 2002-368203 discloses, in a source follower circuit present in a peripheral circuit region of a CCD type photoelectric conversion device, a constitution of electrically connecting a semiconductor region to a gate electrode with an electroconductor buried in a hole arranged in an interlayer insulation layer.
A MOS photoelectric conversion device requires more wiring layers in number than a CCD photoelectric conversion device since one pixel includes a photoelectric conversion element and a plurality of MOS transistors. Here, a light incident aperture of the photoelectric conversion element is defined by the wiring layer. Accordingly, in order to increase optical incidence efficiency to improve sensitivity, a wiring layout for widening the aperture for optical incidence to the photoelectric conversion element will be required.
In order to widen the aperture, in a photoelectric conversion region where a photoelectric conversion element of a MOS photoelectric conversion device is arranged, present inventor has found out to adopt a constitution to electrically connect a semiconductor region to a gate electrode with an electroconductor buried in a hole arranged in an interlayer insulation layer. And, at some occasion of manufacturing a photoelectric conversion device in such a constitution, noises were found to occasionally increase.
Therefore, an object of the present invention is to restrain noise increase being the above described newly found problem and to provide a manufacturing method of a MOS photoelectric conversion device which has been improved in efficiency of optical incidence to a photoelectric conversion element.